Spur from immersion heater socket

[holmslaw]

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[holmslaw]

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[ban-all-sheds]

BAS how do you get a "potential 5KW load" from that arrangement? Afaict other than the lights everything in the garage is going through a 16A MCB.

And the lighting circuit is on a 6A MCB.

16 + 6 = 22.

22 x 230 = 5060.

Hence a potential 5kW load on the spur coming from the socket in the house.

 

[ban-all-sheds]

And of the seven individual 13A sockets, five are fed via a FCU.

Actually it's 6 "individual" sockets, but the number is unimportant. The CU in the garage has a 16A radial circuit with at least one socket outlet on it and a 13A FCU. I say at least one because it isn't clear from the diagram if the double outlet is connected to the load or the supply of the FCU, but again that's unimportant, because however it's connected we have a potential load on that radial of at least 26A.

Banal is having a bad day

No I'm not.

he's desperate to have a go at me in any way possible.

The first is not true, and I'm not having a go - just responding to what you yourself actually wrote.

And the mods have made him remove his insulting comments about people in the plumbing forum.

1) I've made no insulting comments about people in the plumbing forum.

2) The behaviour of Moderator 10 is of no relevance to this.

Poor old BAS, he's so upset he's dragging comments from other threads into this one. If anyone else does it he blows his top.

What I dislike is the practice of dragging irrelevant, off-topic disagreements from one thread to another, or of behaving irrationally towards someone because of grievances from other threads.

In this case, you wrote "The immersion heater should be on it's own dedicated circuit, it is too much load for the ring circuit", and all I did was to say that having it on the ring circuit wasn't really a serious problem.

Because I thought it would be of comfort to the OP I backed that up by observing that portable appliances which would result in 3kW being drawn from a ring were readily available, and that other people apart from me didn't regard a potential 5kW load on a ring as a real problem, let alone a 3kW one. Both of those observations were quite truthful and accurate. The 2nd one can no more be criticised for "dragging comments from other threads into this one" than the 1st can be for dragging the presence of such appliances on other websites onto this one. I did not say that you can get 3kW appliances and here's the evidence, nor did I say that some people thought that potential 5kW loads on one point of a ring circuit were not necessarily unsafe and here's the evidence.

But when you decided to respond to my 2nd observation by saying "'some people' , you mean idiots like you" it seemed quite reasonable to defend myself against that insult by pointing out that it was you yourself who had looked at a potential 5kW load drawn from a single point on a ring and had written that it wasn't necessarily unsafe.

You've advised the OP to carry out work which to be done properly will involve significant expense, and I'm not sure that he really needs to.

If you're going to attempt to discredit an observation which supports the view that expensive changes aren't particularly important to do by saying that it would only be made by an idiot I think it is of great value to the OP for him to know who actually made it.

 

[SUNRAY]

BAS how do you get a "potential 5KW load" from that arrangement? Afaict other than the lights everything in the garage is going through a 16A MCB.

Have you looked as the picture?? No I thought not.


16A + 6A = 22A

22A x 230V = 5060VA or 5.06KVA
22A x 245V [my local voltage] = 5390VA or 5.39KVA

Or another thing, 2 13A loads plugged into a DSSO fed by a 30A or 32A device.

13A x 2 x 245 [my local voltage] = 6.37KVA

In fact this is likely to be higher as the 13A load is generally calculated at 230V and if you go through the calculations that equates as 13.85A or 27.7A for the pair or 6.785KVA.

Lets look at that 3KW heater,
3000 / 230 = 13.04A... mmm
230V / 13.04A = 17.63 ohms
245V / 17.63ohms = 13.89A
245V x 13.89A = 3.404KVA
which takes us up to 27.79A or 6.8KVA at a double socket
253V [maximum permissible] x 17.633ohms = 14.35A or 3.63KVA
which takes us up to 28.7A or 7.26KVA at a double socket.

At that point I feel this part of the discussion should be called to an end in fear of hi jacking the topic, my apologies for cut/paste from a previous post.


Originally putting an immersion heater on a ring circuit was correct and acceptable but now its clearly stated in the regs that it has its own circuit. There is no obligation to meet this regulation however if I were in your position I would be looking into the feasibility of making the change and bringing it up to date, all the time bearing in mind part P requirements.

Edit: the remainder has been added to clarify my intended meaning:

Now with part P the effort required by the OP added to the cost to make the change would probably be infeasible however he is doing some building/decorating works which may possibly involve planning/part P and the circumstances may make it a feasible adjustment.

In my 1966 home the immersion has been used twice since we moved 17 years ago and my wife did not even realise we had one. It was on the ring final when we purchased the house and I only altered it when I was doing other wiring and building works otherwise it would have remained untouched.

2nd edit:
I assume [always silly!] this would appear as a code 4 on a PIR, code 2 if he's a b*****d

 

[ban-all-sheds]

Originally putting an immersion heater on a ring circuit was correct and acceptable but now its clearly stated in the regs that it has its own circuit.

It's clearly advised that one of the measures you can adopt to help ensure compliance with the regulation which requires you to avoid long overloads of parts of ring finals is to put immersion heaters on dedicated circuits, but there's no actual regulation requiring that even now.

But even if there was, as you say there'd be no obligation to make the existing arrangement comply. You can't argue that it wouldn't be the ideal thing to do, or that if starting from scratch it would be the way to go, but old installations are full of things which are not ideal, and decisions to change them have to be informed by how serious a problem they are, and how much it would cost to rectify.

In this situation I don't think it's a serious problem and it would be a non-trivial cost to put in a new circuit. If the OP wants to leave it I don't think he should worry about that decision.

 

[SUNRAY]

Originally putting an immersion heater on a ring circuit was correct and acceptable but now its clearly stated in the regs that it has its own circuit.

It's clearly advised that one of the measures you can adopt to help ensure compliance with the regulation which requires you to avoid long overloads of parts of ring finals is to put immersion heaters on dedicated circuits, but there's no actual regulation requiring that even now.

The old OSG [on site guide] 16th edition clearly states that 'Water heaters fitted to storage vessels in excess of 15 litres capacity,... , are to be supplied by their own separate circuit', this is what I have quoted from and applied as gospel BUT Interestingly there is NO quoted regulation.

But even if there was, as you say there'd be no obligation to make the existing arrangement comply. You can't argue that it wouldn't be the ideal thing to do, or that if starting from scratch it would be the way to go, but old installations are full of things which are not ideal, and decisions to change them have to be informed by how serious a problem they are, and how much it would cost to rectify.

In this situation I don't think it's a serious problem and it would be a non-trivial cost to put in a new circuit. If the OP wants to leave it I don't think he should worry about that decision.

I am in agreement especially as he states it doesn't get used, which is why I commented 'however if I were in your position I would be looking into the feasibility of making the change and bringing it up to date, all the time bearing in mind part P requirements'.

If my previous reply is confusing I am more than happy to edit it to clarify my thoughts.
edit: I have edited my previous post.

 

[plugwash]

Have you looked as the picture?? No I thought not.

yes

16A + 6A = 22A

Ok since the lights are fixed loads I counted the lights at thier actual load (arround 1A) rather than thier breaker rating. That plus the 16A breaker for sockets gives a total of arround 17A

Which is higher than the 13A of a FCU but a lot less than the potential combined load an idiot can draw through a double socket.